Lesson 24: Circumferences and Areas of Circles

The diameter of the large circle above is 2.6 cm. The diameter of each small circle is 0.6 cm. Find the area of the shaded region to the nearest tenth of a centimeter. Use 3.14.

4.18 cm2

To celebrate the new millennium, the Millennium Ferris Wheel was constructed in London, England. The diameter of the wheel is 135 m. What is the circumference of the ferris wheel? Round to the nearest unit.

424 m

The ratio of every circle's area A to the square of its radius r is always the same.

True

Use pi = 3.14 to estimate the area of the circle. Round your answer to the nearest hundredth if necessary. Estimate the diameter of a circle with a circumference of 50 feet.

15.92 ft

Use pi = 3.14 to estimate the area of the circle. Round your answer to the nearest hundredth if necessary. Estimate the diameter of a circle with a circumference of 56 feet.

17.83 ft

The radius of a circular garden is 3.3 inches. Find the circumference. Use pi = 3.14.

20.724 in.

Use pi = 3.14 to estimate the area of the circle. Round your answer to the nearest hundredth if necessary. Estimate the diameter of a circle with a circumference of 80 feet.

25.48 ft

Use pi = 3.14 to estimate the area of the circle. Round your answer to the nearest hundredth if necessary. r = 9.6

289.38 m2

The radius of a circular hat is 4.7 inches. Find the circumference. Use pi = 3.14.

29.516 in.

What is the area of a circle with a diameter that is 20 inches long? Round your answer to the nearest tenth.

314.2 in2

A circular clock face has a diameter of 7 inches. What is the area of the clock face? Round to the nearest tenth.

38.5 in.2

Use pi = 3.14 to estimate the area of the circle. Round your answer to the nearest hundredth if necessary. r = 11.8

437.21 m2

Use pi = 3.14 to estimate the area of the circle. Round your answer to the nearest hundredth if necessary. d = 14.6 cm

45.84 cm

Use pi = 3.14 to estimate the area of the circle. Round your answer to the nearest hundredth if necessary. d = 24.4 m

467.36 m2

What is a reasonable estimate for the area of a circle with radius 4 cm?

48 cm2

Use pi = 3.14 to estimate the area of the circle. Round your answer to the nearest hundredth if necessary. r = 12.8 m

514.46 m2

Use pi = 3.14 to estimate the area of the circle. Round your answer to the nearest hundredth if necessary. r = 9.8 in.

61.54 in.

A pizza has a diameter of 28 cm. What is the area of the pizza rounded to the nearest tenth?

615.8 cm2

What is the area of a circle with a radius of 14 feet?

616 ft2

Use pi = 3.14 to estimate the area of the circle. Round your answer to the nearest hundredth if necessary. r = 14.2

633.15 m2

Find the area of a circle with radius 5 mm, rounded to the nearest tenth.

78.5 mm2

The diameter of a tire is 2.5 ft. Find the circumference of the tire. About how many times will the tire have to rotate to travel 1 mile? (1 mile = 5,280 ft) Show your work.

C = pid = pi(2.5 ft) = 3.14(2.5 ft) = 7.85 ft 5,280/7.85 ft - 672.6 rotations

The front wheel of a high-wheel bicycle from the late 1800s was larger than the rear wheel to increase the bicycle's overall speed. The front wheel measured in height up to 60 cm. Find the approximate circumference of the front wheel of a high-wheel bicycle.

about 188.4 cm

The large stones of Stonehenge are arranged in a circle about 30 m in diameter. Find the area of the circle.

about 707 m2